1. Technical Field
The present invention relates to a method for controlling a liquid ejection apparatus and a liquid ejection apparatus.
2. Background Art
As a liquid ejection apparatus that ejects liquid from a liquid ejection head to a target, an inkjet type printer (hereinafter, referred to as a printer) is known. The printer supplies ink from a cartridge, which retains ink as liquid, to a recording head, or a liquid ejection head, mounted in a carriage. The recording head is then operated to eject the ink onto a sheet of paper, or a target, through nozzles of the recording head.
The printer typically includes a maintenance mechanism. The maintenance mechanism wipes and cleans a nozzle forming surface of the recording head, caps the recording head for preventing the ink from drying in the nozzles, and draws and drains dust and bubbles from the recording head.
A printer described in Japanese Laid-Open Patent Publication No. 2001-1554 includes a valve arranged in an ink passage extending between a cartridge and a recording head. The valve is used in choke cleaning. In the choke cleaning, the valve is closed and a pump is actuated to draw and drain ink from the recording head. This rapidly lowers the pressure in the portion of the passage from the valve to the recording head.
As a result, referring to FIG. 7, negative pressure accumulates in the recording head from the point of time at which suction starts to time TA. At the time TA, the pump is stopped and held in the stopped state until time TB, in such a manner that small bubbles generated by the negative pressure are joined together. At the time TB, the valve is opened to cause a rapid ink flow into the passage, in which the negative pressure has accumulated, instantly increasing the flow speed of the ink. As a result, together with the ink flowing at the increased speed, bubbles and undesirable objects are discharged from the recording head through the nozzles.
Nonetheless, the choke cleaning may cause small bubbles to be caught by a filter arranged between the valve and the recording head. Particularly, if a complicatedly configured recording head or easily foaming ink is employed, the bubbles are easily caught by the filter.
In this case, if the pump is maintained in the stopped state from the time TA to the time TB, joining of the bubbles caught by the filter is not sufficiently promoted. The ink is thus drained through the bubbles on the filter. Also, the bubbles caught by the filter lower the ink supply performance of the recording head or cause flow of bubbles from the nozzles when printing is performed, thus degrading the printing quality.